U.S. patent number 4,604,600 [Application Number 06/740,640] was granted by the patent office on 1986-08-05 for solenoid construction and method for making the same.
This patent grant is currently assigned to G. W. Lisk Company, Inc.. Invention is credited to Bruce D. Clark.
United States Patent |
4,604,600 |
Clark |
* August 5, 1986 |
Solenoid construction and method for making the same
Abstract
A proportional solenoid has a fixed pole piece 39 and a movable
armature 45, both fitted into the bore 52 of a guide tube 36 that
provides the required concentricity between the fixed and movable
pole pieces 39 and 45. One of the pole pieces has a cylindrical
recess 56 and the other pole piece has a reduced diameter
cylindrical nose 62 that is complementary to cylindrical recess 56.
A radially inwardly facing frusto-conical surface 95 is formed in
cylindrical nose 62 to be disposed within recess 56 of the other
pole piece and provide a frusto-conical pole piece section
producing a linear force-stroke curve.
Inventors: |
Clark; Bruce D. (Clifton
Springs, NY) |
Assignee: |
G. W. Lisk Company, Inc.
(Clifton Springs, NY)
|
[*] Notice: |
The portion of the term of this patent
subsequent to September 3, 2002 has been disclaimed. |
Family
ID: |
24977433 |
Appl.
No.: |
06/740,640 |
Filed: |
June 3, 1985 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
563891 |
Dec 23, 1983 |
4539542 |
|
|
|
Current U.S.
Class: |
335/261; 335/279;
335/281 |
Current CPC
Class: |
H01F
7/13 (20130101); H01F 7/1607 (20130101); H01F
7/16 (20130101); H01F 2007/085 (20130101) |
Current International
Class: |
H01F
7/16 (20060101); H01F 7/08 (20060101); H01F
7/13 (20060101); H01F 007/08 () |
Field of
Search: |
;335/251,255,257,261,262,279,258,268,281 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Harris; George
Attorney, Agent or Firm: Stonebraker, Shepard &
Stephens
Parent Case Text
RELATED APPLICATIONS
This is a continuation-in-part companion application to my parent
application Ser. No. 563,891, filed Dec. 23, 1983, now U.S. Pat.
No. 4,539,542 entitled SOLENOID CONSTRUCTION AND METHOD FOR MAKING
THE SAME. A patent on this application will expire at the same time
as a patent on my parent application.
Claims
I claim:
1. An assembly for use in a solenoid comprising:
a. a hollow solenoid armature tube adapted to be received in a
solenoid coil, said tube having an armature chamber therein;
b. a stationary pole piece member fixed in and defining one end of
said armature chamber;
c. an armature member positioned in said armature chamber of said
tube for axial sliding movement relative to and defining an
armature stroke relative to said pole piece member;
d. one of said members having an axially extending recess therein
and the other member having a reduced in cross section end portion
adapted to be received in and complementary to said recess;
e. said other member having a radially internally facing
frusto-conical surface formed on said reduced in cross section end
portion and disposed within said recess;
f. said armature tube having a non-magnetic section defining a
reduced magnetic gap extending coaxially with at least a portion of
said armature stroke sufficient to permit selected magnetic forces
to be produced on said armature; and
g. said armature tube providing concentricity of said two
members.
2. An assembly in accordance with claim 1 in which said armature
tube comprises a one-piece metal tube.
3. An assembly in accordance with claim 1 including non-magnetic
bearing means between said armature member and said armature tube
for reducing friction.
4. An assembly in accordance with claim 3 in which said bearing
means provides a non-magnetic space between said armature member
and said armature tube.
5. An assembly in accordance with claim 4 in which said bearing
means comprises multiple circumferential bearing surfaces spaced
linearly along said armature.
6. An assembly in accordance with claim 1 in which said stationary
pole piece member has a reduced in cross section part adapted to be
received in and mate with the internal surface of one end of said
armature tube.
7. An assembly in accordance with claim 1 in which said armature
tube comprises a one-piece semi-austenitic material tube treated to
be non-magnetic along said non-magnetic section of said tube.
8. An assembly in accordance with claim 1 in which said armature
tube comprises a non-magnetic one-piece tube.
9. An assembly in accordance with claim 1 in which said armature
tube comprises a non-magnetic metal one-piece tube.
10. An assembly in accordance with claim 1 wherein said one member
has a radially externally facing frusto-conical surface surrounding
said recess and extending into said chamber.
11. An assembly for use in a solenoid comprising:
a. a hollow solenoid armature tube adapted to be received in a
solenoid coil, said tube having an armature chamber therein;
b. a stationary pole piece member fixed in and defining one end of
said armature chamber;
c. an armature member positioned in said armature chamber of said
tube for axial sliding movement relative to and defining an
armature stroke relative to said pole piece member;
d. one of said members having an axially extending recess therein
and the other member having a reduced in cross section end portion
adapted to be received in and complementary to said recess;
e. said other member having a radially internally facing
frusto-conical surface formed on said reduced in cross section end
portion and disposed within said recess;
f. said armature tube having a non-magnetic section means providing
a reduced magnetic gap extending coaxially with at least a portion
of said armature stroke sufficient to permit selected magnetic
forces to be produced on said armature; and
g. said armature tube providing concentricity of said two
members.
12. An assembly in accordance with claim 11 in which said armature
tube comprises a one-piece metal tube.
13. An assembly in accordance with claim 11 in which said
stationary pole piece member has a reduced in cross section part
adapted to be received in and mate with the internal surface of one
end of said armature tube.
14. An assembly in accordance with claim 11 in which said armature
tube comprises a one-piece semi-austenitic material tube treated to
be non-magnetic along said non-magnetic section of said tube.
15. An assembly in accordance with claim 11 in which said armature
tube comprises a non-magnetic metal one-piece tube.
16. An assembly in accordance with claim 11 wherein said one member
has a radially externally facing frusto-conical surface surrounding
said recess and extending into said chamber.
17. An assembly for use in a solenoid comprising:
a. a one-piece cylindrical metal hollow solenoid armature tube
adapted to be received in a solenoid coil, said tube having a
cylindrical armature chamber therein;
b. a stationary pole piece member fixed in and defining one end of
said armature chamber;
c. a cylindrical armature member positioned in said armature
chamber of said tube for axial sliding movement defining a stroke
gap relative to and defining an armature stroke relative to said
pole member;
d. one of said members having an axial concentric cylindrical
recess therein and the other cylindrical member having a reduced in
cross section axial cylindrical concentric and portion adapted to
be received in and complementary to said recess;
e. said other member having a radially internally facing
frusto-conical surface formed on said reduced in cross section end
portion and disposed within said recess;
f. said armature tube having a non-magnetic section means providing
a reduced magnetic gap extending coaxially with at least a portion
of said armature stroke sufficient to permit selected magnetic
forces to be produced on said armature; and
g. said armature tube providing concentricity of said two
members.
18. An assembly in accordance with claim 17 including non-magnetic
bearing means between said armature member and said armature tube
for reducing friction.
19. An assembly in accordance with claim 18 in which said bearing
means provides a non-magnetic space between said armature member
and said armature tube.
20. An assembly in accordance with claim 19 in which said bearing
means comprises surfaces spaced linearly along said armature.
21. An assembly in accordance with claim 17 in which said
stationary pole piece member has a reduced in cross section part
adapted to be received in and mate with the internal surface of one
end of said armature tube.
22. An assembly in accordance with claim 17 in which said armature
tube comprises a one-piece semi-austenitic material tube treated to
be non-magnetic along said non-magnetic section of said tube.
23. An assembly in accordance with claim 17 including a solenoid
coil surrounding said armature tube.
24. An assembly in accordance with claim 17 wherein said one member
has a radially externally facing frusto-conical surface surrounding
said recess and extending into said chamber.
25. A method of providing an assembly for use in a solenoid
comprising the steps of:
a. providing a hollow solenoid armature tube adapted to be received
in a solenoid coil, said tube having an armature chamber
therein;
b. providing a stationary pole piece member fixed in and defining
one end of said armature chamber;
c. providing an armature member positioned in said armature chamber
of said tube for axial sliding movement relative to and defining an
armature stroke relative to said pole piece member;
d. providing one of said members with a recess therein and the
other member with a reduced in cross section end portion adapted to
be received in and complementary to said recess;
e. providing said other member with an internally facing
frusto-conical surface formed on said reduced in cross section end
portion and disposed within said recess;
f. providing said armature tube with a non-magnetic section
defining a reduced magnetic gap extending coaxially with at least a
portion of said armature stroke sufficient to permit selected
magnetic forces to be produced on said armature; and
g. said armature tube providing concentricity of said two
members.
26. A method in accordance with claim 25 in which said armature
tube is provided as a one-piece metal tube.
27. A method in accordance with claim 25 including the step of
providing a non-magnetic bearing means between said armature member
and said armature tube for reducing friction.
28. A method in accordance with claim 27 in which said bearing
means is provided as a non-magnetic space between said armature
member and said armature tube.
29. A method in accordance with claim 25 in which said bearing
means is provided as multiple circumferential bearing surfaces
spaced linearly along said armature.
30. A method in accordance with claim 25 in which said stationary
pole piece member is provided with a reduced in cross section part
adapted to be received in and mate with the internal surface of one
end of said armature tube.
31. A method in accordance with claim 25 in which said armature
tube is provided as a one-piece semi-austenitic material tube
treated to be non-magnetic along said non-magnetic section of said
tube.
32. A method in accordance with claim 25 including providing a
solenoid coil surrounding said armature tube.
33. A method in accordance with claim 25 including providing said
one member with an externally facing frusto-conical surface
surrounding said recess and extending into said chamber.
Description
BACKGROUND
1. Field of the Invention
This invention relates to solenoids and methods for making the same
and particularly proportional type solenoids.
2. Description of the Prior Art
General purpose solenoids provide a force-stroke curve whereby the
force at a closed stroke gap is higher than the force developed at
the initial starting stroke gap. These solenoids are sometimes
referred to as "on-off" solenoids and are energized ("on") to a
fully operated position or are de-energized ("off") to a fully
neutral position. In this type of solenoid, in order to activate
the armature to close the stroke gap, the solenoid must only
provide enough force to overcome the load including any frictional
or side-loading magnetic forces perpendicular to the axis of
motion.
Proportional solenoids have long been known in the art to provide a
force vs. stroke curve that allows the output force of the solenoid
to be proportional to the electrical current applied to the coil.
This proportionality of the output force permits such a solenoid to
either fully or partially operate a load by selectively applying
either the full or a partial electrical current to the solenoid
coil and thereby may selectively position the armature along the
linear distance of the gap.
In order to operate this type of solenoid accurately, the forces in
the solenoid must be accurately controlled. Since the frictional
and side loading forces vary depending upon a number of factors
that cannot be accurately controlled, including tolerances in
manufacturing and the equipment being operated by the solenoid,
desirably their effects should be minimized in the design of the
solenoid.
The prior art history of proportional solenoids and problems of
such solenoids are described in U.S. Pat. No. 3,900,822, Column 1
(Hardwick).
The prior art proportional solenoid provided multiple complex
bearing surfaces including a bearing between the armature rod and
the stationary pole piece. For example, see the complex bearing and
structural support for the armature in each of the prior art
patents, German Pat. No. 1,270,178 and U.S. Pat. Nos. 3,870,931 and
3,970,981, in order to provide the necessary structure for a
proportional solenoid and to provide concentricity of the armature.
Such constructions required very fine manufacturing tolerances, and
it was difficult assembling such solenoids.
In order to overcome the concentricity problems of the above prior
art patents and provide a concentricity tube for maintaining
concentricity of both the armature and fixed pole piece, a multiple
section armature tube 10 as shown in FIG. 1 of the drawings was
invented. This multiple section tube 10 included a magnetic section
12 made of ferromagnetic material having an external frusto-conical
surface 14. The next section of the tube is a non-magnetic brass
ring 16 brazed or otherwise permanently fixed at the surface 14 to
section 12 and is brazed or permanently fixed along an opposite
frusto-conical surface 18 to a third section 20 made of
ferromagnetic material. Thus, the non-magnetic brass ring middle
section 16 provides the essential non-magnetic radial transverse
frusto-conical gap, which gap is linearly coextensive with the
stroke gap of the armature. The tube 10 is press fitted or
otherwise permanently fixed to a stationary or fixed magnetic pole
piece 22 made of ferromagnetic material. The composite armature
tube 10 and stationary pole piece 22 are received and mounted in a
solenoid coil (not shown).
A movable armature 24 made of ferromagnetic material is provided
with a pair of spaced non-magnetic bearing surfaces 26 made by
bronze bushings, for example. There is a non-magnetic shim 28
surrounding a push rod 30 permanently mounted on armature 24 and
slidable in a center hole 32 of the stationary pole piece 22.
The construction of the three-section tube shown in FIG. 1 is
similar to the construction shown in U.S. Pat. No. 3,970,981 except
that all three sections are brazed or otherwise fixed together to
form one continuous multiple section, multiple metal armature
tube.
SUMMARY OF THE INVENTION
The present invention includes a hollow solenoid armature tube
adapted to be received in a solenoid coil, a stationary pole piece
member fixed in one end of the tube, an armature member adapted for
axial sliding movement in the tube, one of the members having an
axially extending recess therein and the other of the members
having a reduced in cross section end portion adapted to be
received in and complementary to said recess. The member having the
reduced in cross section end portion also has a radially internally
facing frusto-conical surface formed within the recess, the tube
thereby providing concentricity of the two members, and the tube
having a non-magnetic section extending coaxially with the gap made
by the stroke of the armature.
The present invention minimizes the concentricity problems with
proportional type solenoids with a less complicated structure than
prior art solenoids. This is done by containing both the stationary
pole piece and the movable armature within the same cylindrical
surface of a single metal armature guide tube.
The present invention pertains to proportional type solenoids. It
is an object of this invention to provide an improved solenoid
construction overcoming the problems of the prior art as described
above.
It is an important object of this invention to reduce the effects
of magnetic side loading with simpler structure than the prior art.
This is done by controlling the concentricity between a reduced
diameter cylindrical nose of the movable armature and the mating
cylindrical recess in a stationary pole piece. Concentricity is
maintained because both the movable armature and the stationary
pole piece are confined by the bore of a one-piece metal guide
tube.
It is further an object of this invention to minimize magnetic side
loading by providing a non-magnetic space between most of the
linear dimensions of the armature and the adjacent magnetic
members, which can be provided by at least several alternatives
such as a uniform non-magnetic bearing surface or simply making the
entire guide tube non-magnetic.
DRAWINGS
FIG. 1 is a cross-sectional view of a prior art solenoid tube and
pole pieces;
FIG. 2 is a cross-sectional view of one embodiment of the present
invention with a solenoid coil and housing added;
FIG. 3 is a cross-sectional view of a portion of a second
embodiment of the present invention;
FIG. 4 is a graph showing the force-stroke performance of the
solenoid provided by the present invention; and
FIGS. 5-8 are fragmentary, cross-sectional views of alternative
preferred embodiments of the present invention.
DETAILED DESCRIPTION
The preferred embodiment of the invention illustrated in FIG. 2 is
a general purpose proportional solenoid. The construction of the
present invention is readily adaptable to proportional solenoids
requiring a pressure tight bore such as those solenoids used in
hydraulic applications. Also, this invention is readily adaptable
to push-pull solenoids. The illustrated embodiment includes an
outer housing 31 made of ferromagnetic material. An end washer 32
and an end washer 33 made of ferromagnetic material are press
fitted into the housing 31. The housing 31 and end washers 32 and
33 encase an electrical winding or coil 34 that is wound on a coil
form (bobbin) 35.
A concentricity guide tube or hollow solenoid armature tube 36 is
preferably a one-piece metal tube made of magnetic stainless steel
material, defining a cylindrical armature chamber 29 adapted to
receive an armature 45 made of ferromagnetic material. The armature
45 is adapted to slide axially in the armature chamber 29. The
armature tube 36 has a cylindrical non-magnetic middle section 37
(described more in detail hereinafter).
In the embodiments of FIGS. 2-3 and 5-8, the armature tube 36 is
preferably made of semiaustenitic steel (as described more in U.S.
Pat. No. 3,633,139), such as that known as 17-7P.H. (precipitation
hardening) stainless steel. The non-magnetic (austenitic) section
37 provides hindrance to that portion of the magnetic field trying
to pass through the non-magnetic section 37 of the armature tube
36, thereby providing a gap which is reduced in magnetic force
described more in detail hereinafter. The remainder of the armature
tube 36 on both sides of the non-magnetic section 37 is magnetic
(martensitic) in order to minimize hindrance of the magnetic field
passing radially therethrough. Or, the armature tube 36 may be
entirely non-magnetic, when the armature tube wall thickness is
thin enough to keep the magnetic losses sufficiently small to allow
the solenoid to operate with the desired efficiency.
Although from a manufacturing point of view it would be more
expensive and therefore less desirable, it would be possible within
the concept of this invention to provide a welded or brazed
together multiple section tube having at least one non-magnetic
section extending axially along the desired gap, which is reduced
in magnetic force, in lieu of the one-piece tube 36, and still
fulfill the concept and functions of this invention.
There is a stationary pole piece 39 fixed in one end of the
armature tube 36 thereby defining one end of the armature chamber
29. In the embodiment of FIG. 2, stationary pole piece 39 has a
radially externally facing frusto-conical section 41 having a
radially externally facing frusto-conical surface 54 that is
annular and concentric to the center axis of the tube and that
surrounds an axial cylindrical concentric recess 56 (that is also
concentric to the tube axis) of the stationary pole piece 39.
Stationary pole piece 39 has a center bore 58 adapted to receive a
non-magnetic push rod 60 permanently mounted on the armature 45.
Bore 58 and push rod 60 are not necessary if the solenoid is
designed for pulling, rather than pushing. The stationary pole
piece 39 is made of ferromagnetic material and has a linear section
with a reduced outside diameter 50 which is press fitted into a
bore 52 of the armature tube 36.
Thus, both the stationary pole piece 39 and the movable armature 45
are maintained in concentricity by the armature tube 36. The
armature 45 is shown in FIG. 2 in solid line in its energized
position and is shown in FIG. 2 in broken line at 45A in its
de-energized or "neutral" position.
The non-magnetic section 37 of the armature tube 36 surrounds an
air gap 38. The armature 45 has a reduced in cross section axial
cylindrical concentric end portion or nose 62 surrounded by a
shoulder 42. The reduced in cross section portion 62 is received in
and complementary to the cylindrical recess 56 of the stationary
pole piece 39. The shoulder 42 of movable armature 45 (as
illustrated in the retracted position at 42A and as shown in broken
line on the armature in the retracted broken line position 45A)
defines the air gap 38 which extends axially to the radially
externally facing frusto-conical section 41 of the stationary pole
piece 39.
The non-magnetic section 37 and air gap 38 in the FIG. 2
illustrated embodiment each extend coaxially from an internal
radial end surface 40 of armature 45 represented by the line B to
the line D (of FIG. 2), which is the shoulder 42A when the armature
45 is in its de-energized broken line position. In this embodiment,
the non-magnetic section 37 and air gap 38 exceed the full stroke
of the armature illustrated in FIG. 2, which full stroke is between
the lines B and E and includes a "working stroke" between the lines
B to C of FIG. 2 and an "overtravel" stroke between the lines C and
E of FIG. 2. The force characteristics of each of these strokes are
described hereinafter with reference to FIG. 4 which illustrates
these force characteristics.
Thus, the non-magnetic section 37 of the tube provides a gap which
is reduced in magnetic force, shown in FIG. 2 between the lines B
to D (hereinafter referred to as reduced magnetic gap) illustrated
so that in the present embodiment the reduced magnetic gap is
coaxially the same as the air gap 38, thereby also extending
between the lines B and D of FIG. 2; thus is provided a reduced
magnetic gap coaxially longer than the full stroke of the armature
which extends only between the lines B and E of FIG. 2. It will be
understood by one skilled in the art that the coaxial distance of
the non-magnetic section 37 can be selectively varied in order to
permit the desired selected magnetic forces to be produced on the
armature 45 in order to get the resulting desired selected
proportional forces output and forces curve. One such desired curve
is shown in FIG. 4; other curves can be obtained as desired. As
already described, the armature tube 36 may be constructed of
completely non-magnetic material such as non-magnetic stainless
steel. What is important is that the non-magnetic section 37 of the
armature tube 36 extends coaxially at least a selected portion of
the armature stroke sufficient to permit selected magnetic forces
to be produced on the armature 45 to get the desired selected
proportional forces output and curve.
An external cylindrical surface 46 of the armature 45 is provided
with a pair of cylindrical spaced uniform non-magnetic bearing
surfaces 64 made by electroless nickel plating. Thus, a uniform
non-magnetic space is provided between the armature 45 and the
armature tube 36, which minimizes the effects of frictional and
side-loading forces. A non-magnetic brass shim 66 is provided to
eliminate the portion of the stroke which yields undesirable rising
force characteristics as illustrated by that portion of the curve
on the FIG. 4 graph between the lines A to B.
The graph illustrated in FIG. 4 shows a typical force vs. stroke
curve for the FIG. 2 solenoid which has a 20 ohm coil with a size
of 1.75 inch outside diameter, 2 inches long, and an 0.88 inch
diameter bore. The forces shown by the solid line 74 between the
lines E and C (FIG. 4) are termed "overtravel" stroke and are used
when additional stroke gap is required beyond the "working" stroke
gap C-B. The additional stroke gap may be required for some other
use, for example on a double-solenoid hydraulic valve. The force
shown by solid line 72 between the lines C and B of FIG. 4 shows a
substantially constant force characteristic which illustrates the
force during the solenoid "working" stroke as the armature 45 moves
from the partially energized "C" position of FIG. 2 toward the
fully energized (solid line) "B" position of FIG. 2. The broken
line force, shown by the curve or line 70 between lines B and A
(FIG. 4) is generally undesirable and is eliminated as described
above by inserting the shim 66.
FIG. 3 illustrates a portion of a second embodiment of this
invention in which the relative positions of the radially
externally facing frusto-conical surface 54 (FIG. 2) and recess 56
(FIG. 2) of the stationary pole piece 39 are reversed. Thus, a
radially externally facing frusto-conical surface 76 is provided on
armature 78 of FIG. 3 and likewise there is a corresponding
reversal of the parts by incorporating a reduced in cross section
cylindrical end portion or nose 84 corresponding to the nose piece
62 of FIG. 2 on a stationary pole piece 82 of FIG. 3. The radially
externally facing frusto-conical surface 76 surrounds an axial
cylindrical concentric recess 80 corresponding to the recess 56 of
the stationary pole piece 39 in FIG. 2. The armature 78 and the
stationary pole piece 82 are maintained in concentricity by an
armature tube 86. The rest of the structure of the FIG. 3
embodiment is the same as in the FIG. 2 embodiment.
Fixed and movable pole pieces arranged within an armature tube to
have a complementary recess and reduced in cross section end
portion disposed within the recess offer possibilities for
frusto-conical pole piece sections other than the externally facing
frusto-conical surfaces surrounding a pole piece recess as
explained above relative to FIGS. 2 and 3. These other
frusto-conical pole piece sections were envisioned as possibilities
when my parent application was filed and have now been confirmed by
experimentation to be practical. My preferred embodiments of these
alternatives are shown in FIGS. 5-8.
All these alternatives share the basic structure explained above
relative to FIGS. 2 and 3, including fixed and movable pole pieces
concentrically aligned within armature tube 36 and preferably using
the same solenoid components and structure as described in more
detail above. These alternatives also share with the embodiments of
FIGS. 2 and 3 the basic structure of a recess 56 formed in the end
of one pole piece, and a complementary projection or nose 62 formed
in the other pole piece to be disposed within the recess 56.
Alternative frusto-conical pole piece sections can then be formed
relative to complementary recesses and end projections as shown in
FIG. 5 for a conic section formed on movable armature 45a and in
FIG. 6 for a conic section formed on fixed pole piece 39b. Instead
of having a conic section with a radially externally facing
frusto-conical surface surrounding recess 56a of fixed pole piece
39a of FIG. 5 or recess 56b of movable armature 45b of FIG. 6, the
reduced in cross section end portion or nose 62a or 62b
complementary to recess 56a or 56b is formed with a radially inward
facing frusto-conical surface 95 disposed within recess 56a or 56b.
This arrangement, like the embodiments shown in FIGS. 2 and 3, can
also produce a proportional solenoid with a force-stroke curve
having a linear portion such as shown in FIG. 4.
Pole pieces 45a, 39a, 45b, and 39b, are otherwise concentrically
aligned within armature tube 36 as previously explained, and the
rest of the solenoid structure preferably uses the same components
as described in more detail relative to the embodiment of FIG. 2.
These include a washer-shaped shim 66a between armature shoulder 42
and fixed pole piece 39a or 39b to limit the approach together of
the fixed and movable pole pieces for the same purpose as shim 66
in the embodiment of FIG. 2. Also included are push rod 60
extending through bore 58 in a fixed pole piece, although this is
not used for pull-type solenoids.
I have discovered further that pairs of opposed and confronting
conic sections between fixed and movable pole pieces as shown in
FIGS. 7 and 8 can also produce a proportional solenoid. Movable
armature 45a of the embodiment of FIG. 7 is similar to the movable
armature 45a of the embodiment of FIG. 5, but fixed pole piece 39c
has an externally facing frusto-conical surface 54a surrounding
recess 56a, similar to frusto-conical surface 54 of the embodiment
of FIG. 2. The frusto-conic sections that overlap and move relative
to one another between inward facing frusto-conical surface 95 and
outward facing frusto-conical surface 54a can produce a
force-stroke curve with a linear section as shown in FIG. 4.
A stop device must limit the approach of movable armature 45a
toward fixed pole piece 39c; and since there is no room for a
conventional shim 66, such as used in the embodiments of FIGS. 2,
3, 5, and 6, I prefer abutment pins or a stop collar 96 secured to
push pin 60.
The embodiment of FIG. 8 reverses the configuration of FIG. 7, with
recess 56b formed in movable armature 45c and reduced cross section
end piece or nose 62a formed in fixed pole piece 39b. This disposes
radially inwardly facing frusto-conical surface 95 within recess
56b, which is surrounded by radially outwardly extending
frusto-conical surface 54a. The effect is similar to the solenoid
of FIG. 7.
The invention has been described in detail above with particular
reference to preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention as described hereinabove and
as defined in the appended claims.
* * * * *